Simplify the following expression: $k = \dfrac{15p}{10r - 30p} - \dfrac{20p + 5}{10r - 30p}$ You can assume $p,q,r \neq 0$.
Since the expressions have the same denominator we simply combine the numerators: $k = \dfrac{15p - (20p + 5)}{10r - 30p}$ $k = \dfrac{-5p - 5}{10r - 30p}$ The numerator and denominator have a common factor of $5$, so we can simplify $k = \dfrac{-p - 1}{2r - 6p}$